1. Field of the Invention
The present invention relates to an inkjet recording apparatus and recording method, and more particularly, to control technique for an inkjet recording apparatus using a line head wherein a plurality of recording elements are arranged in one direction.
2. Description of the Related Art
Recently, inkjet recording apparatuses (inkjet printers) have become common as recording apparatuses for printing and recording images captured by digital still cameras, and the like. Inkjet recording apparatuses are relatively inexpensive, and not only are they straightforward to use, they also have the merit of yielding images of good quality. An ink-jet recording apparatus comprises a plurality of recording elements in a head, the recording head scanning a recording medium while droplets of ink are ejected toward the recording medium from the recording elements, and each time one line of an image is recorded onto recording paper, the recording medium is conveyed through a distance corresponding to one line, this process being repeated, whereby an image is formed onto the recording paper.
Inkjet printers include those which use a fixed-length serial head, and carry out recording by moving the head to scan a recording medium in the lateral direction of the recording medium, and those which use a line head in which recording elements are aligned up to a dimension corresponding to the full width of one edge of the recording medium. In a printer using a line head, it is possible to carry out image recording across the full surface of the recording medium, by scanning the recording medium in an orthogonal direction to the direction in which the recording elements are arranged. In a printer using a line head, it is not necessary to provide a conveyance system, such as a carriage, or the like, for moving a short-dimension head to scan the recording medium, and furthermore, movement of the carriage and complex scanning control of the recording medium also becomes unnecessary. Furthermore, since only the recording medium is moved, it is possible to achieve increase the recording speed in comparison to printers using serial heads.
In the recording device and control method disclosed in Japanese Patent Application Publication No. 10-157135, a plurality of nozzle rows for making the same line are provided, and ink is ejected as droplets onto a recording medium, by selective use of these nozzle rows.
Moreover, in the inkjet printer disclosed in Japanese Patent Application Publication No. 10-235854, a device for causing a nozzle row provided in a line head to oscillate is provided, whereby the visual perception of streaks of unevenness is lessened by causing the nozzle row to oscillate very slightly in the direction of alignment of the nozzle row. Furthermore, the aforementioned reference also discloses an embodiment wherein ink is ejected while causing the head to move in the direction of alignment of the nozzle row, and an embodiment wherein ink is ejected while causing the recording paper to move in the direction of alignment of the nozzle row.
In the printing method for an inkjet printing apparatus disclosed in Japanese Patent Application Publication No. 2000-326497, the visual perception of streaks of unevenness is lessened by increasing the dot size ejected, at uniform intervals.
However, in an inkjet recording apparatus which comprises a fixed row of nozzles which cover the full width of the image area, and which performs image recording by conveying the recording medium in a direction orthogonal to the row of nozzles, then since the drawing of a line parallel to the direction of conveyance is carried out by means of a single nozzle only, if there is variation in the dot position due to fluctuation in the direction of ejection from each nozzle, or the like, then a streak of unevenness in the direction of conveyance is likely to be perceived in the image.
In the recording apparatus disclosed in Japanese Patent Application Publication No. 10-157135, since a plurality of nozzle rows are provided, the number of nozzles is increased by the corresponding multiple, and therefore costs and the maintenance burden are markedly increased.
Moreover, in the inkjet printer disclosed in Japanese Patent Application Publication No. 10-235854, not only is it necessary to provide a high-precision mechanism for causing minute oscillation of the nozzle rows, thereby leading to high costs, but furthermore, there is also the concern that image quality is degraded by the minute oscillations.
In the printing method for an inkjet printing apparatus disclosed in Japanese Patent Application Publication No. 2000-326497, it is necessary to provide complex control of the image processing, and furthermore, adverse affects, such as poorer granularity in the output image, occur.